Physical Sciences Research Highlights

Corralling Xenon Gas Out of Waste Streams

Metal-organic frameworks, with nanopores and a high affinity for xenon, can separate the gas from air or waste streams. Xenon has applications in various fields including lighting, space propulsion and medicine. Image courtesy of Pacific Northwest National LaboratoryEnlarge Image.

From space propulsion to lighting to surgical anesthesia, the applications
and needs for xenon gas are growing. And the good news is that researchers are
advancing the science to more easily remove xenon from waste streams and
collect the low amounts of it found in the atmosphere.

Researchers at DOE's Pacific Northwest National Laboratory are at the forefront of
research developing porous nanoscale materials to capture xenon. They report in
the journal Chem
that inexpensive materials called metal-organic frameworks have been very
successful in separating the gas in a way that may make it far less expensive
than existing means of producing it.

Currently, industry uses a common but expensive process called cryogenic
distillation to separate xenon from other gases or the atmosphere. In that
costly process, a lot of energy is used to chill entire gas streams down to far
below freezing to concentrate the xenon.

"The process we've demonstrated to selectively trap xenon in a MOF can
be done at room temperature," said Dr. Praveen Thallapally, a materials
scientist at PNNL and a corresponding author on the paper. "You pass a
mixed gas stream over the MOF materials just one time to capture the xenon and
it can be stored long term and easily released for industrial applications when
you want to use it."

The paper's authors note that xenon would likely be used more if it was more
economical to produce. For instance, they point to reports that show xenon is
considered a better surgical anesthetic than the existing technology as it is
more potent, less risky, more environmentally friendly and potentially
recyclable.

MOFs, while nano-sized, have a high surface area and are full of pores that can
suck up gases like sponges suck up water. There are thousands of MOFs that
exist and can be created but each need to be tuned or optimized to attract and
hold different gases of interest.

Researchers at PNNL, in collaboration with other research groups, optimized
the properties of a MOF material called SBMOF-1 and demonstrated that it
selectively traps xenon and, in a second pass, can also trap krypton, both of
which are byproducts of nuclear reprocessing. Much of this research is funded
by DOE's Office of Nuclear Energy to explore technologies that may one day
enable safe, efficient recycling of nuclear fuel.

The PNNL team patented its separation process and is interested in
partnering with companies to do additional testing or licensing of the
technology. For more information on licensing or collaboration contact Sara Hunt.